1. Technical Field
The present disclosure relates to a relay, and more particularly, to a relay having a single movable contact with respect to two stationary electrodes.
2. Background
In an electric vehicle, a battery disconnect unit is used to supply a DC electric power from a battery to an inverter or interrupt the electric power supply.
The battery disconnect unit includes two main relays for positive and negative direct current (DC) supplying paths, and one pre-charge relay for protecting the main relays from an inrush current.
The pre-charge relay serves to temporarily switch on to protect the main relays from an inrush current generated when an electric vehicle is started.
Some embodiments of the present disclosure may be applied to such a pre-charge relay, but is not limited to this. That is, some embodiments of the present disclosure may be applied to various types of relays.
A relay 100 in accordance with the conventional art will be explained with reference to FIGS. 1 to 9.
Referring to FIG. 1, the conventional relay 100 has a rectangular parallelepiped shape, and includes main circuit terminals 1 formed at an upper part thereof and control signal receiving terminals 2 formed at a lower part thereof. The main circuit terminals 1 are exposed to the front side in a protruding manner, and are connected to a main circuit for supplying a direct current. And the control signal receiving terminals 2 are exposed to the front side in a protruding manner, and are configured to receive a control signal to open or close the relay 100 (so called, a magnetizing control signal). The control signal to open or close the relay 100 may be provided as a voltage signal of DC 12V.
Referring to FIG. 1, reference numeral 50 denotes an enclosure to accommodate therein components of the conventional relay 100.
The relay according to some embodiments of the present disclosure may have the same or similar appearance as or to the conventional relay shown in FIG. 1, and thus showing of the appearance of the relay according to some embodiments of the present disclosure will be omitted.
The inner configuration of the conventional relay 100 will be explained with reference to FIGS. 2 to 6.
Referring to FIG. 6, the conventional relay 100 comprises an upper mechanism assembly 20, a movable part assembly 30, a magnetic coil assembly 40, an enclosure 50, and a lower cover 60.
As shown in FIG. 3, the upper mechanism assembly 20 includes main circuit terminals 1, stationary contacts 3, ferromagnets 12, a return spring 13, an upper cover 21, insulating supporting portions, etc.
FIG. 3 illustrates a configuration of the upper mechanism assembly 20, which shows the upper mechanism assembly 20 upside down. The upper mechanism assembly 20 is assembled with other components with a posture shown in FIG. 6.
The main circuit terminals 1 have conductor parts of a thin bar shape. Although not shown in FIG. 3 due to the insulating supporting portions, the conductor parts extend to the inside of the relay 100 passing through the upper cover 21. In FIG. 3, contact parts visible below the stationary contacts are partial regions of the conductor parts.
The stationary contacts include one stationary contact connected to a positive side main circuit terminal 1 and another stationary contact connected to a negative side main circuit terminal 1. And the pair of stationary contacts are welded on the contact parts of the main circuit terminals 1, respectively.
The ferromagnet 12 is configured with a permanent magnet having a ferromagnetism. And two ferromagnets are formed on right and left sides of each stationary contact 3. The ferromagnets 12 extinguish an arc generated when movable contacts 4 are separated from the stationary contacts, by inducing the arc to sides of the stationary contacts 3 and the movable contacts 4 by a magnetic flux generated nearby.
The return spring 13 has one end supported by the insulating supporting portions between the pair of stationary contacts 3, and another end supported by a recessed portion formed at an upper end of the movable part assembly 30. And the return spring 13 provides an elastic force to the movable part assembly 30, in a direction that biases the movable part assembly 30 to be far from the stationary contact 3. Thus, once a coil (refer to reference numeral 6 in FIG. 2 or FIG. 5) of the magnetic coil assembly 40 is demagnetized, the movable part assembly 30 returns to the original position spaced from the stationary contacts 3.
The upper cover 21, configured to shield inner components of the relay 100 from the outside, shields the upper mechanism assembly 20 and the movable part assembly 30 which are disposed at an upper part and a middle part of the pre-charge relay 100, from the outside. The upper cover 21 is differentiated from the lower cover 60 configured to shield the magnetic coil assembly 40 disposed at a lower part of the relay 100 from the outside.
The insulating supporting portions, configured to electrically insulate and support inner extending parts of the main circuit terminals 1 of the relay, the ferromagnets 12, the return spring 13, etc., may be formed of a synthetic resin material having an electrical insulating property.
As shown in FIG. 4, the movable part assembly 30 includes a shaft 5, a movable contact arm 4a, a contact spring 7, and a movable core 10.
The shaft 5, a cylindrical member including an upper part having a large diameter and a lower part having a small diameter, may be formed of an electric insulating material.
The upper part having a large diameter of the shaft 5 includes a recessed portion which supports a lower end of the return spring 13; a hollow portion disposed below the recessed portion to accommodate the contact spring 7 therein; and an opening formed in front and rear directions in order to allow inserting the movable contact arm 4a thereinto, and open in a vertical direction by a predetermined length.
The lower part having a small diameter of the shaft 5 has a predetermined outer diameter which may be forcibly-inserted into the inner diameter portion of the movable core 10.
The shaft 5 and the movable core 10 may be coupled to each other as the lower part having a small diameter of the shaft 5 is forcibly-inserted into the inner diameter portion of the movable core 10. In the coupled state, the shaft 5 and the movable core 10 are able to move together to the same direction.
The movable contact arm 4a is configured with a metallic plate formed of a conductive material such as copper. As shown in FIG. 4, the movable contact arm 4a is penetratingly-inserted into the opening of the shaft 5. And the movable contact arm 4a is installed such that a central part thereof in a lengthwise direction receives an elastic pressure in upward direction from the contact spring 7 disposed therebelow, for contacting with an upper part of the opening.
The movable contacts 4 are installed on an upper surface of two ends of the movable contact arm 4a in a lengthwise direction, by welding.
The contact spring (in other words “contact pressure spring”) 7, as a compression spring is installed in the hollow portion of the shaft 5. An upper end of the contact spring 7 supports the central part of the movable contact arm 4a in a lengthwise direction, and a lower end of the contact spring 7 is supported by a bottom surface of the hollow portion of the shaft 5.
Thus, the contact spring 7 can be compressed or extended to the original state, in the hollow portion of the shaft 5.
The movable core 10 can be formed with a cylindrical hollow iron core.
As shown in FIG. 2 or FIG. 7, a rubber pad 11 can be forcibly-inserted into a lower end of the movable core 10, for coupling with the movable core 10.
The rubber pad 11 can be provided to attenuate collision noise and an impact generated when the movable core 10 collides with an inner bottom surface of the enclosure 50 when it returns to the lower original position by the return spring 13, when the magnetic coil assembly 40 is demagnetized.
The shaft 5 and the movable core 10 are coupled to each other as the lower part having a small diameter of the shaft 5 is forcibly-inserted into the hollow portion of the movable core 10.
The movable core 10 is magnetized by a magnetic field applied from the magnetic coil assembly 40, and upward-moves in a repulsing manner by a magnetic field of a vertical direction applied from the magnetic coil assembly 40 or is demagnetized together with the magnetic coil assembly 40 when the magnetic coil assembly 40 is demagnetized. Then, the movable core 10 downward-moves by an elastic force of the return spring 13 applied to an upper end of the shaft 5.
As shown in FIG. 5, the magnetic coil assembly 40 comprises a bobbin 8, a coil 6, a yoke 9 and control signal receiving terminals 2.
The bobbin 8 includes a body portion having a hollow cylindrical shape to allow the movable core 10 to be inserted thereinto or to be separated therefrom, and flange portions formed at upper and lower ends of the body portion and configured to determine a winding limit of the coil 6. The coil 6 is wound on the body portion.
The coil 6 is wound on the body portion of the bobbin 8, and is magnetized or demagnetized according to whether a control signal is applied to the control signal receiving terminals 2 or not.
As shown in FIG. 2, the yoke 9 is formed to enclose the bobbin 8, and provides a circulation path of a magnetic flux generated from the coil 6 when the coil 6 is magnetized.
Referring to FIGS. 2 and 5, the control signal receiving terminals 2 are installed to pass through the wound coil 6. When a control signal is received through the control signal receiving terminals 2, the coil 6 is magnetized by the control signal. And the coil 6 is demagnetized when the reception of the control signal is stopped.
Referring to FIG. 1, FIG. 2 or FIG. 6, the enclosure 50 provides a means to accommodate therein the components of the pre-charge relay 100, and may be formed of a synthetic resin material having an electrical insulating property. As shown in FIG. 6, the enclosure 50 may be formed as a rectangular parallelepiped member having one open surface and five closed surfaces, and having an empty inner space, in order to accommodate the components of the relay 100 therein.
Referring to FIG. 6, the lower cover 60, a cover to shield the inner components of the relay 100 from the outside, shields the magnetic coil assembly 40 positioned at a lower part of the relay 100 from the outside. The lower cover 60 is different from the upper cover 21 which shields the upper mechanism assembly 20 and the movable part assembly 30 which are disposed at an upper part and a middle part of the relay 100, from the outside.
The lower cover 60 has two openings formed to correspond to the control signal receiving terminals 2, such that the control signal receiving terminals 2 are exposed to the outside through the openings.
An operation of the relay 100 in accordance with the conventional art will be explained in brief.
Referring to FIG. 2, in an ‘off’ state of the relay 100, once a control signal is applied through the control signal receiving terminals 2, the coil 6 is magnetized. In this case, the movable core 10 is also magnetized by a vertical magnetic field applied from the coil 6, thereby moving upward.
Then, the shaft 5 of which lower part has been coupled to the movable core 10 moves upward together with the movable core 10, with overcoming an elastic force of the return spring 13. As a result, the movable contact arm 4a supported by the shaft 5 and the contact spring 7 also moves upward.
The two movable contacts 4 welded on the upper surface of two ends of the movable contact arm 4a move upward to contact the pair of stationary contacts 3 (‘ON’ state). Such an ‘ON’ state of the relay is shown in FIG. 7.
As a closed circuit is formed from the positive side main circuit terminal 1 to the stationary contact 3, the movable contacts 4, the movable contact arm 4a, the stationary contact 3, and the negative side main circuit terminal 1, a conducting path from the positive side main circuit terminal 1 to the negative side main circuit terminal 1 may be formed. And a direct current may be supplied through the relay 100.
In the ‘on’ state shown in FIG. 7, if supply of a control signal through the control signal receiving terminals 2 is stopped, the coil 6 is demagnetized, and the vertical magnetic field provided from the coil 6 disappears. Further, since the movable core 10 is also demagnetized, the upward-driving force of the movable core 10 disappears.
Then, the shaft 5 moves downward by an elastic force of the return spring 13, the elastic force applied to an upper end of the shaft 5. As a result, the movable contact arm 4a supported by the shaft 5 and the contact spring 7 also moves downward.
The two movable contacts 4 welded on the upper surface of two ends of the movable contact arm 4a move downward to be separated from the pair of stationary contacts 3 (‘OFF’ state). Such an ‘off’ state is shown in FIG. 2.
In the ‘off’ state, the conducting path from the positive side main circuit terminal 1 to the negative side main circuit terminal 1 is broken, and supply of a direct current through the relay 100 is stopped.
An electromagnetic repulsive force generated around the contacts during an initial stage of the ‘on’ operation will be explained with reference to FIG. 8.
As shown in FIG. 8, a current introduced through the stationary contact 3 (the left) connected to the positive side main circuit terminal, flows out through the movable contact arm 4a and the stationary contact 3 (the right), sequentially. Since a direction of the incoming current (11) (the lower side) and a direction of the outgoing current (12) (the upper side) are opposite to each other, an electromagnetic repulsive force to push the movable contact arm 4a from the stationary contacts is generated between the contacts (refer to the arrow indicating ‘F’).
An arc generated between the movable contact arm 4a and the stationary contacts 3 by a magnetic field (B) from the ferromagnets 12, receives outward pushing forces such as ‘F1’ and ‘F2’.
This may cause a chattering phenomenon that the movable contacts contact the stationary contacts and then are separated from the stationary contacts, repeatedly, during an initial stage of an ‘on’ operation.
The pre-charge relay is a means to bypass an initial inrush current generated when an electric vehicle is started. Such a chattering phenomenon delays a time to bypass an initial inrush current. This may cause the main relays of the battery disconnect unit to be damaged by the inrush current, and may shorten the lifespan of the relay.
The conventional pre-charge relay has the following problems.
As shown in FIG. 2 or FIG. 7, since only a central part of the movable contact arm 4a is supported by the contact spring 7, the two movable contacts 4 contact the two stationary contacts 3 in a very unbalanced state. This may cause only the movable contact 4 and the stationary contact 3 of one side, to be abraded. As a result, a basic performance of the pre-charge relay (a function to bypass an initial inrush current) may not be desirably executed.